Retrieval of nearshore bathymetry from Sentinel-2A and 2B satellites in South Florida coastal waters

TLDR

The study evaluates Sentinel‑2A/B MSI for generating bathymetric maps via a ratio transform model in South Florida. Atmospheric correction is performed with ACOLITE, vertical calibration uses 5–10 ground points from digital charts, and validation is conducted against lidar surveys. Satellite‑derived bathymetry achieves median absolute errors of 0.5 m (West Palm Beach), 0.4 m (Key West), and 0.22 m (Dry Tortugas) in low‑turbidity conditions, demonstrating accurate mapping with a fast, flexible, and economical solution that captures small‑scale features and remains robust even with generic calibration.

Abstract

This study examines the relatively high-resolution MultiSpectral Instrument (MSI) onboard Sentinel-2A and 2B for generating bathymetric maps through a ratio transform model in South Florida (United States). Atmospheric correction of imagery is implemented though ACOLITE software, providing accurate performance and consistency over different Sentinel-2A/B scenes and three different study sites. Vertical calibration uses 5–10 points collected from digital charts, independent of lidar surveys, which are used for validation and error analysis. Satellite-Derived Bathymetry (SDB) has Median Absolute Error (MedAE) of 0.5 m in West Palm Beach (at depths ranging between 0 and 18 m, limit of lidar survey for validation), 0.4 m in Key West (0–5 m), and 0.22 m in Dry Tortugas (0–6 m), in conditions with low turbidity. Accurate bathymetry mapping can be accomplished with both sensors over environments with varying water transparency conditions, with the advantage of a fast, flexible, and economical solution. The 10-m MSI can capture small-scale features, such as tidal channels, straits relevant to navigation or steep slopes. While the least error is achieved by calibrating each image separately, a generic calibration produces only a moderately greater error with MedAE still ∼1m, indicating the robustness of the approach. The research highlights the great potential of the 5-day revisit, suggesting that the twin Sentinel-2 mission of the Copernicus programme may enhance SDB to leverage its use for several operational purposes, particularly in remote and inaccessible regions of the world.